Gallup finds Romney leading by 6 points among those who have already voted

According to a Gallup survey, Mitt Romney leads President Obama by 6 points (52-46) among those who have already voted. Gallup found that 15 percent of registered voters have cast their ballots.

At one level, Romney’s 6 point margin among those who have already voted isn’t surprising. According to Gallup, he has almost the same margin (51-46) among likely voters as a whole.

On the other hand, at the corresponding stage in 2008, Gallup found that Obama led John McCain in early voting by 15 points (55-40). Since Obama’s final margin over McCain was much smaller, it may be that Romney’s 6 point margin among those who have already voted this year understates his edge over the president.

I suspect, however, that McCain’s underperformance with early voters reflected a lack of enthusiasm for the candidate, and high enthusiasm for Obama. Romney doesn’t suffer from that problem. Many of his supporters can’t wait to vote against Obama. Meanwhile, it’s unlikely that Obama supporters are quite as enthusiastic about him as they were four years ago.

If I’m right, then we shouldn’t expect Romney’s margin to expand as more votes are cast. On the other hand, it doesn’t need to. A 6 point margin would be enough.